Yes, it should be fine. If you still have doubts, test a little on a piece of scrap sprue. If it doesn't craze the sprue, it is okay to use. Testors enamel paints are pretty tame compared to hotter solvent paints, such as lacquers and acrylic enamels used for full size cars. But even those can be used if the parts are coated with a good quality primer first.
Only thing to keep in mind is that gloss Testors paints tend to take awhile to cure fully on plastic, so after painting you might want to cover up the parts for a few days before handling the parts to finish up construction or do decalling. Flat paints will dry to the touch a lot more quickly by comparison.